Individuals with partial or complete paralysis of the lower extremity use a knee-ankle-foot orthosis (KAFO) for ambulation and must have the knee locked for stability during gait. Use of a KAFO results in lack of knee movement during the swing phase of gait and increased energy expenditure to walk, resulting in a high rejection rate by users. An electronically controlled knee joint has been developed that can be installed on a conventional KAFO. This design uses modular electronics to sense limb loading and activate a clutch control mechanism at the knee. The knee joint unlocks during the swing phase and looks during the stance phase of gait. The goal of phase I is to demonstrate the feasibility of an alternative clutch mechanism which is smaller and delivers higher torque capability. The Phase I study is expected to establish proof of feasibility and prepare for further Phase II development and clinical testing. If successful, the energy efficient knee-ankle-foot orthosis will be manufactured and marketed by a recognized leader in orthotic/prosthetic equipment. This type of brace will be useful for patients with poliomyelitis, spinal cord injuries, myopathic disorders, congenital spinal defects, and acquired paralysis due to infections or vascular insults. PROPOSED COMMERCIAL APPLICATION: This system is for use by persons with mobility limitations. It will restore, replace or enhance the function of children and adults with physical disabilities of the lower extremity. Currently, there are about 866,000 people who use a leg brace. The dissatisfaction with conventional KAFO's result in a rejection rate of 60- 100%. These individuals would benefit from the brace being developed in this research project.